iran crane's president mahmoud ahmadinejad flashed a peace sign to the u.n. today but war is on the front burner, one opening discussed launching a preemptive strike against israel if the jewish state is poised to attack. the unthinkable dilemma. what would the u.s. do if iran attacked or threatened israel or israel preemptively attacked iran. romney is using the many challenges in the region to paint the president as weak. >> look at are entire context. assassination, 20,000 people killed in syria. iran close to becoming a nuclear nation. these are far from bumps in the road. >> reporter: the president responded with a challenge of his own. >> if governor romney is suggesting that we should start another war, then he should say so. >> reporter: and tomorrow morning, diane, president obama will address the u.n. assembly a senior administration official said the president will reiterate his firm commitment to making sure iran does not obtain a nuclear weapon. diane. >>> all right, jake, thank you. as you know, while the president is in new york at the united n